Weber syndrome is a classic midbrain stroke syndrome characterized by ipsilateral cranial nerve III (oculomotor) palsy with contralateral hemiparesis, caused by a lesion involving the ventral midbrain — specifically the oculomotor nerve fascicles and the cerebral peduncle.[1-2] It is most commonly caused by midbrain infarction secondary to occlusion of perforating branches of the posterior cerebral artery (PCA) or upper basilar artery.[1][3-4]

1. History

Acute onset of diplopia, ptosis, and eye deviation (eye "down and out" on the affected side)
Simultaneous or rapidly progressive contralateral limb weakness (arm, leg, ± face)
Timing: sudden onset suggests vascular etiology; subacute onset raises concern for mass lesion, abscess, or demyelination[1][5]
Ask about preceding TIA symptoms: vertigo, visual changes, dysarthria, ataxia, drop attacks
Headache (may suggest hemorrhage or mass effect)
Recent trauma, infection, or immunosuppression (tuberculoma, abscess)[1][6]
Important negatives: no seizure activity, no altered mental status (unless extensive lesion), no preceding fever

2. Alarm Features

Rapidly declining consciousness — suggests basilar artery occlusion or expanding hemorrhage[7-8]
Bilateral motor deficits or quadriparesis — suggests bilateral midbrain or extensive brainstem involvement
Respiratory irregularity or hemodynamic instability — brainstem compression
Locked-in syndrome features (preserved consciousness with quadriplegia and anarthria)
Acute severe headache — hemorrhagic etiology
Fever with neurological deficits — brainstem abscess or tuberculoma[1][6]

3. Medications

Acute ischemic stroke: IV alteplase (0.9 mg/kg) within 4.5 hours of symptom onset; tenecteplase is now FDA-approved for acute ischemic stroke. The EXPECTS trial demonstrated benefit of alteplase for posterior circulation stroke up to 24 hours after onset[9-10]
Antiplatelet therapy: aspirin 325 mg within 24–48 hours if thrombolytics not given
Anticoagulation if cardioembolic source identified (after acute phase)
Contraindicated: anticoagulants and antiplatelets within 24 hours of thrombolysis
Statin therapy for secondary prevention
If tuberculoma: antitubercular therapy ± systemic steroids[1]
If Behçet's disease: corticosteroids[11]

4. Diet

NPO initially until dysphagia screening is completed[12]
Heart-healthy/DASH diet for long-term secondary stroke prevention
Sodium restriction if hypertensive
Adequate hydration to maintain euvolemia; avoid dehydration which may worsen ischemia

5. Review of Systems

Neurologic: vision changes, diplopia, ptosis, facial droop, limb weakness/numbness, dysarthria, dysphagia, ataxia, vertigo
Cardiovascular: palpitations, chest pain (atrial fibrillation as embolic source)
Constitutional: fever, weight loss, night sweats (tuberculosis, malignancy)[1][5]
Rheumatologic: oral/genital ulcers, skin lesions (Behçet's disease)[11]
Infectious: recent illness, immunosuppression

6. Collateral History and Family History

Time last known well — critical for thrombolytic eligibility
Witnessed symptom onset vs. wake-up stroke
Baseline functional status (pre-morbid modified Rankin Scale)
Family history of stroke, coagulopathy, or connective tissue disorders
Social history: smoking, alcohol use, illicit drug use (cocaine, amphetamines)
History of tuberculosis exposure or endemic area travel[1]

7. Risk Factors

Hypertension — most significant risk factor for small-vessel disease and lipohyalinosis causing midbrain lacunar infarcts[13]
Diabetes mellitus
Atrial fibrillation (cardioembolic source)[4][14]
Hyperlipidemia
Smoking
Intracranial atherosclerotic disease — particularly relevant in Asian populations[15]
Basilar artery stenosis[3]
Coagulopathy (e.g., hemophilia — reported cause of midbrain hemorrhage leading to Weber syndrome)[16]
Vasculitis (Behçet's disease, SLE)[5][11]

8. Differential Diagnosis

Benedikt syndrome: CN III palsy + contralateral tremor/involuntary movements (red nucleus involvement rather than cerebral peduncle)[2]
Claude syndrome: CN III palsy + contralateral ataxia + tremor (superior cerebellar peduncle + red nucleus)[2]
Nothnagel syndrome: CN III palsy + ipsilateral cerebellar ataxia[2]
Posterior communicating artery aneurysm: isolated CN III palsy (pupil-involving) without hemiparesis
Uncal herniation: CN III palsy with contralateral hemiparesis — mimics Weber syndrome but from supratentorial mass effect
Cavernous sinus lesion: CN III palsy ± other cranial neuropathies (IV, V1, V2, VI)
Myasthenia gravis: fluctuating ptosis/diplopia without hemiparesis
Brainstem tumor (glioma, lymphoma, metastasis)[5]
Demyelinating disease (MS, NMOSD, MOGAD)[5]

9. Past Medical History

Prior stroke or TIA (especially posterior circulation)
Hypertension, diabetes, hyperlipidemia, atrial fibrillation
Known intracranial atherosclerotic disease or vertebrobasilar stenosis
Bleeding disorders[16]
Autoimmune/inflammatory conditions (Behçet's, sarcoidosis, SLE)[5][11]
History of tuberculosis[1]
Prior cardiac surgery or prosthetic valves

10. Physical Exam

Vital signs: hypertension (permissive in acute stroke unless >220/120), tachycardia (atrial fibrillation), fever (infectious etiology)

Eyes (ipsilateral to lesion)

Ptosis
Eye deviated "down and out" (lateral strabismus with depression)
Dilated, fixed pupil (if complete CN III palsy)
Impaired adduction, elevation, and depression of the eye

Motor (contralateral to lesion)

Upper motor neuron pattern hemiparesis (face, arm, leg)
Increased tone, hyperreflexia, positive Babinski sign
Cerebellar exam: typically normal unless lesion extends
Assess for dysarthria and dysphagia
NIHSS for stroke severity scoring[12][17]

11. Lab Studies

Stat glucose (required before thrombolysis)[17]
CBC, BMP, coagulation studies (PT/INR, aPTT)
Troponin (concurrent cardiac event)
Lipid panel, HbA1c
ESR/CRP if vasculitis or infection suspected
Blood cultures if febrile
Hypercoagulability workup in young patients without traditional risk factors
TB testing (QuantiFERON, PPD) if tuberculoma suspected[1]

12. Imaging

Non-contrast CT head: first-line to exclude hemorrhage; often normal in early midbrain infarction[18]
MRI brain with DWI: gold standard — demonstrates restricted diffusion in the ventral midbrain (cerebral peduncle). MRI is far more sensitive than CT for posterior fossa lesions[3][19-20]
CT angiography (CTA) or MR angiography (MRA): evaluate for posterior cerebral artery occlusion, basilar artery stenosis/occlusion, or vertebral artery disease[4][21]
CT perfusion: may help identify salvageable tissue in extended time windows[10]
Imaging is unnecessary to repeat if the diagnosis is established and the patient is clinically stable

13. Special Tests

NIHSS: standard stroke severity assessment; note that NIHSS has limitations in posterior circulation strokes[17]
pc-ASPECTS (Posterior Circulation ASPECTS): 10-point scale assessing extent of posterior circulation ischemia on CT/MRI[15][22]
Echocardiography (TTE ± TEE): evaluate for cardioembolic source (PFO, valvular disease, intracardiac thrombus)
Telemetry/Holter monitor: screen for paroxysmal atrial fibrillation
Carotid/vertebral duplex ultrasound or dedicated vessel imaging
Lumbar puncture: if infectious or inflammatory etiology suspected[11]

14. ECG

Obtain 12-lead ECG to evaluate for

Atrial fibrillation/flutter — most common cardioembolic source
Acute MI (concurrent event)
Left ventricular hypertrophy (chronic hypertension)
Continuous cardiac monitoring for at least 24 hours recommended[12]

15. Assessment

Weber syndrome is a crossed brainstem syndrome localizing to the ventral midbrain, where the oculomotor nerve fascicles traverse the cerebral peduncle.[2] The most common etiology is ischemic stroke from occlusion of paramedian perforating branches of the PCA or upper basilar artery.[1][3-4] Less common causes include hemorrhage, tuberculoma, neoplasm, demyelination, and vasculitis.[1][5][11][16] Classic brainstem syndromes like Weber syndrome rarely occur in their pure form.[21] The prognosis of isolated midbrain infarction is generally favorable, except in cases of bilateral involvement.[19]

16. Treatment Plan

Acute stabilization: ABCs, IV access, cardiac monitoring, continuous pulse oximetry
Thrombolysis: IV alteplase (0.9 mg/kg, max 90 mg; 10% bolus, remainder over 60 min) if within 4.5 hours of symptom onset. Alteplase may benefit posterior circulation stroke patients up to 24 hours after onset based on the EXPECTS trial[10]
Endovascular thrombectomy: for large-vessel occlusion (basilar artery) within 24 hours per AHA/ASA 2026 guidelines; ATTENTION and BAOCHE trials demonstrated superiority of EVT over medical management[15][22]
Blood pressure management: permissive hypertension (do not treat unless >220/120 if no thrombolysis); if thrombolysis given, maintain BP <185/110 pre-treatment and <180/105 post-treatment[12]
Antiplatelet therapy: aspirin 325 mg within 24–48 hours (if thrombolytics not administered)
Glucose management: target 140–180 mg/dL[12]
DVT prophylaxis: intermittent pneumatic compression in immobile patients[12]
Dysphagia screening before oral intake[12]
Secondary prevention: statin, antihypertensives, anticoagulation if AF identified
Non-vascular etiologies: treat underlying cause (antitubercular therapy, corticosteroids for Behçet's, antibiotics for abscess)[1][6][11]

17. Disposition

All patients with Weber syndrome require admission — typically to a stroke unit or neuro-ICU[12][23]
ICU admission criteria: declining consciousness, respiratory compromise, large infarct burden, post-thrombolysis/thrombectomy monitoring, hemodynamic instability
Neurology consultation mandatory; neurosurgery consultation if hemorrhagic etiology or mass lesion
Transfer to a comprehensive stroke center if EVT capability is unavailable locally[17]
Patients with bilateral brainstem infarction or basilar artery occlusion carry significantly worse prognosis[4][14]

18. Follow Up / Return Precautions

Inpatient: serial neurological assessments (NIHSS trending), repeat imaging at 24 hours post-thrombolysis, cardiac monitoring for ≥24 hours
Post-discharge follow-up: neurology within 1–2 weeks; ophthalmology if persistent CN III palsy; cardiology if AF or cardiac source identified
Rehabilitation: early physical/occupational/speech therapy referral
Return precautions: new or worsening weakness, vision changes, difficulty speaking or swallowing, severe headache, altered consciousness
Expected course: prognosis for isolated midbrain infarction is generally good; CN III palsy may partially or fully recover over weeks to months; contralateral hemiparesis recovery depends on infarct extent[19]
Long-term: optimize vascular risk factors, medication adherence, lifestyle modification
Relevant images 3 items
Forest plot for Forest plot for successful recanalization, complete recanalization, and first‐pass effect.
CNS Neuroscience & Therapeutics January 31, 2023
Distribution of Scores on the Modified Rankin Scale at 90 Days (Intention-to-Treat Population).
NEJM April 2, 2025
Endovascular Complications and Angiographic Outcomes Stratified by Vessel Segment
JAMA Neurol March 31, 2021

References

1. Weber Syndrome Secondary to Brain Stem Tuberculoma. — Parija S, Lalitha CS, Naik S. Indian Journal of Ophthalmology. 2018.

2. Pearls & Oy-Sters: Looking Up the Anatomy of Looking Up. — Abid MB, Soon D, Rathakrishnan R, et al. Neurology. 2016.

3. Pure Midbrain Infarction: Clinical Syndromes, MRI, and Etiologic Patterns. — Bogousslavsky J, Maeder P, Regli F, Meuli R. Neurology. 1994.

4. Mesencephalic and Associated Posterior Circulation Infarcts. — Kumral E, Bayulkem G, Akyol A, et al. Stroke. 2002.

5. Clinical Reasoning: A 60-Year-Old Man With Rapidly Progressive Left Hemibody Weakness and Vision Loss. — Rock M, Shipley SC, Little JN, Berger JR, Xu DJ. Neurology. 2025.

6. Ethmoid Abscess With Findings Simulating Weber Syndrome. — Luo JJ, Jacobson M, Kamal AK, Azizi SA. Neurology. 2005.

7. Basilar Artery Occlusion. — Mattle HP, Arnold M, Lindsberg PJ, Schonewille WJ, Schroth G. The Lancet. Neurology. 2011.

8. Endovascular Management of Acute Stroke. — Nguyen TN, Abdalkader M, Fischer U, et al. Lancet. 2024.

9. FDA Orange Book. — FDA Orange Book. 2026.

10. Alteplase for Posterior Circulation Ischemic Stroke at 4.5 to 24 Hours. — Yan S, Zhou Y, Lansberg MG, et al. The New England Journal of Medicine. 2025.

11. A Case of Behçet's Disease With Weber's Syndrome. — Emura A, Takeuchi A, Hashimoto T, et al. The Journal of Rheumatology. 1986.

12. Acute Ischemic Stroke. — Powers WJ. The New England Journal of Medicine. 2020.

13. Clinical Reasoning: A 74-Year-Old Woman Presenting With Monocular Ptosis and Binocular Diplopia. — Liu Z, Zhang WW, Dai P, et al. Neurology. 2023.

14. Midbrain Infarction: Associations and Aetiologies in the New England Medical Center Posterior Circulation Registry. — Martin PJ, Chang HM, Wityk R, Caplan LR. Journal of Neurology, Neurosurgery, and Psychiatry. 1998.

15. 2026 Guideline for the Early Management of Patients With Acute Ischemic Stroke: A Guideline From the American Heart Association/American Stroke Association. — Prabhakaran S, Gonzalez NR, Zachrison KS, et al. Stroke. 2026.

16. Weber Syndrome Caused by Intracerebral Hemorrhage in a Hemophiliac Boy. — Mizuguchi M, Kano H, Narita M, Chen RF, Bessho F. Brain & Development. 1993.

17. Care of the Patient With Acute Ischemic Stroke (Prehospital and Acute Phase of Care): Update to the 2009 Comprehensive Nursing Care Scientific Statement: A Scientific Statement From the American Heart Association. — Ashcraft S, Wilson SE, Nyström KV, et al. Stroke. 2021.

18. Acute Stroke Diagnosis. — Choi EY, Nieves GA, Jones DE. American Family Physician. 2022.

19. Pure Midbrain Infarction: Clinical, Radiologic, and Pathophysiologic Findings. — Kim JS, Kim J. Neurology. 2005.

20. Teaching NeuroImages: Stroke Presenting With Isolated Superior Branch of Cranial Nerve III Palsy. — Kapoor G, Shah YD, Libman R. Neurology. 2020.

21. Posterior Circulation Ischaemic Stroke and Transient Ischaemic Attack: Diagnosis, Investigation, and Secondary Prevention. — Markus HS, van der Worp HB, Rothwell PM. The Lancet. Neurology. 2013.

22. Trial of Thrombectomy 6 to 24 Hours after Stroke Due to Basilar-Artery Occlusion. — Jovin TG, Li C, Wu L, et al. The New England Journal of Medicine. 2022.

23. Recommendations for the Management of Cerebral and Cerebellar Infarction With Swelling: A Statement for Healthcare Professionals From the American Heart Association/American Stroke Association. — Wijdicks EF, Sheth KN, Carter BS, et al. Stroke. 2014.

24. Aspiration versus stent retriever for posterior circulation stroke: A meta‐analysis. — Guo X, Xiong Y, Huang X, et al. CNS Neuroscience & Therapeutics. 2023.

25. Thrombectomy for Primary Distal Posterior Cerebral Artery Occlusion Stroke: The TOPMOST Study. — Meyer L, Stracke CP, Jungi N, et al. JAMA Neurology. 2021.